Gravity concentrator for metallurgical materials



Jan. 24, 1961 H. P. RocK ETAL Y 2,969,147

GRAVITY CONCETRATOR FOR METALLURGICAL MATERIALS Filed Sept. l2, 1956 3 Sheets-Sheet 1 HOWARD l? ROCK CLYDE S. TOONE Jan.24, 1961 HROCK ETAL 2,969,147

GRAVITY CONCENTRATOR FOR METALLURGICAL MATERIALS Filed Sept. 12, 1956 5 Sheets-Sheet 2 N Q I Q 1 Q lo l fi ff t [n INVENTOR.

" HOWARD P ROCK CLYDE s. TOONE ATTORNEYS Jan. 24, 1961 H P, ROCK E TAL 2,969,147

GRAVITY CONCENTRATOR FORMETALLURGICAL MATERIALS Filed Sept. 12, 1956 3 Sheets-Sheet 3 b' la INVENTOR. HOWARD E ROCK CLYDE S. TOOIIE GRAVITY CONCENTRATOR FOR METAL- LURGICAL MATERIALS Howard P. Rock, Cisco, Utah, and Clyde S. Toone, 641 N. Redwood Road, Salt Lake City, Utah Filed Sept. 12, 1956, Ser. No. 609,476

`14 Claims. (Cl. 209-437) This invention relates to metallurgical concentrating equipment for effecting separation between mineral particles of different specific gravities.

Many kinds of equipment of the type concerned have been developed in the past and are being extensively used at present by the metallurgical industry.

The gravity concentrator of this invention is structurally and functionally unique in many respects over anything known heretofore, and is capable of accomplishing results not heretofore possible with machines land apparatus utilizing the force of gravity as t..e separating agency.

Among the objects of the invention are to achieve an exceptionally clean and complete separation of very finely divided metallic particles, such as flour gold, from vgangue materials with which they are intimately associvated in nature; to effect an efficient separation of a variety of different finely divided solid materials from lignter materials with which they are mixed; and to provide apparatus for such purposes that is econonLcal to construct, maintain, and operate.

The principal feature of the gravity concentrator of the invention is an elongate deck, perforated by a longitudinally extending series of mutually spaced and .transversely extending slits which are exceptionally narrow at the upper surface of the deck and serve to draw off relatively heavy fines that tend to hug such deck surface as a mineral pulp is flowed upon and along it.

Further objects and features of the invention will become apparent from the following detailed description of .a preferred specific embodiment thereof, as illustrated by way of example in the accompanying drawings.

In the drawings:

Fig. l represents a side elevation of a gravity concen- .trator unit of the invention as incorporated in gravity `concentrating apparatus for recovering flour gold from placer sands;

Fig. 2, a top plan view of the unit of Fig. 1;

Fig. 3, an end elevation;

Fig. 4, a fragmentary, longitudinal, vertical section taken on t'he line 4-4 of Fig. 2 and greatly enlarged;

Fig. 5, a still further enlarged view of the portion of Fig. 4, comprehended by the broken line 5;

Fig. 6, a transverse vertical section taken on the line 6 6 of Fig. 2;

Fig. 7, a diagrammatic layout in end elevation of the complete gravity concentrating apparatus in which the unit of the preceding figures is incorporated; and

Fig. 8, the same layout in side elevation looking from the right in Fig. 7. I

Referring to the drawings:

The invention may be embodied in many different forms of apparatus for industrial utilization, depending upon the particular application. As mentioned previously herein, the invention is particularly useful in the recovery of flour gold from placer sands. Accordingly, apparatus for that purpose is here illustrated and described, though it should be realized that mineral pulps Patented Jan. 24, 1961 generally may be advantageously handled by various constructions of apparatus incorporating the essential concepts of the invention.

The gravity concentrating apparatus shown schematically in Figs. 6 and 7 is made up of a number of individual, longitudinally inclined, gravity, concentrator units 10 arranged in tiers 11, there being five tiers in the illustrated instance.

The individual tiers may include as many of the individual concentrator units 10 in longitudinally side-by-side arrangement as deemed suitable for a particular installation, the number decreasing from the upper tiers to the lower, and usually only a single unit being provided for the bottom tier or tiers. In this way, the concentrator units of the upper tier serve as roughers, while those of each succeeding tier serve as cleaners working on the concentrates obtained from the preceding tier or tiers.

In the illustrated instance, material to be treated is fed to the several rougher concentrator units 10 of the uppermost tier through respective pipes 12a leading from a distributor feeder 12, it being understood that the material has been initially screened and formed into a thin aqueous pulp by the addition of an abundance of water. Launders 13, extending transversely of the concentrate discharge ends of the several concentrator units 10 of the respective tiers, serve to catch the concentrates discharged therefrom and pass them, by way of respective chutes or spouts 13a, to feed boxes 14 of the respective concentrator units of the next lower tier. The waste gangue is washed from the lower ends of the concentrator decks of the respective units into any suitable disposal system- (not illustrated), while t"e final cleaned concentrate flows from the concentrate discharge of the single concentrator unit 1f) of the bottom tier, for collection and further processing where necessary.

Water is utilized to wash the eoncentzates from the individual concentrator units 10 and along the several launders 13 to final discharge as the finished concentrate. For this purpose, supply pipes 15 extend from a water main 16 to the respective concentrator units.

Each of the gravity concentrator units 10 is of elongate formation, and comprises a flow channel defined by a pair of mutually spaced side walls 18 and by a bottom wall 19 of unusual character. Such bottom wall 19 provides, in effect, a deck upon and along whose fiat and smooth upper surface 19a flows an aqueous pulp of the material to be treated. Such deck surfaces 19a receives a stream of pulp at its upper end from feed box 14 (which is preferably rigidly joined to walls 18 and 19) and discharges a stream of gangue from its lower, discharge end.

Immediately below the bottom wall or deck 19, an elongate trough 21 of desirably V-shape is provided for catching concentrates passing through such deck by reason of elongate slit openings 22 provided therein.

The slit openings 22 advantageously extend transversely of the length of the deck 19 and of the flow pulp thereover, and are preferably provided in mutually spaced, series formation from end to end 0f such deck.

Each of the slit openings 22 has a width determined by the requirements of the particular material to be treated and by whether the gravity concentrator unit concerned is a rougher or a finisher. In all instances the slit openings are exceptionally attenuate, for the purpose of the invention is to bleed off only enough of the liquid from the rapidly flowing stream to wash the heaviest fines through such openings; but the rougher units will have wider openings than the finisher units, and the recovery lof such finely divided values as flour gold will involve ,gold vfrom placer sands and a width of -six thousandths Amost satisfactory for finishing purposes, although as high as approximately fifteen thousandths may' be used for ,roughing purposes and as low as approximately three thousandths for finishing purposes.

These are the widths .at the deck surface, and are the eective widths for bringing about the desired separation of valued fines from gangue. However, in order to insure passage `through such slit openings of enough of the lcarrier liquid to keep the way open, the slit openings increase in Width along their depths.

As illustrated in Fig. 5, the desired 'attenuate width extends downwardly to a limited extent, so there will be -suflcient thickness of material adjacent the deck surface to resist wear. This defines an entryway 22a having uniform width along its depth. The width then gradually increases along the depth to define a divergent outlet 22b, which is advantageously of inverted and truncated V-formation lin right cross-section.

As mentioned above, by so conigurating such slit openings 22 that they increase in width from top to bottom, the possibility of clogging during operation of the equipment is almost completely precluded.

As illustrated, see particularly Fig. 6, it is preferred to construct the bottom wall or deck 19 of trough 2l from a series of slat plates 26' of some rigid and wear-resistant material, such as stainless steel, having straight and smooth edges. Such plates are placed side by side between and supported by the side walls i8 of the trough, the slit openings 22 being dened between adjoining longitudinal edges thereof. Y In order to enable the widths of the slits 22 to be established at close tolerance, it is desirable that the longitudinal edges of the slat plates 20 be machined to the beveled edge surfaces required for defining the respective slits; and, in order to provide for differential vibration of the individual plates relative to one another, it is advantageous that such plates be individually joined to the side walls 18 of the trough by welding.

The gravity concentrator 10 as so formed is mounted on structural supports 23 of a suitable supporting framework (not shown as such), so as to slope downwardly from its feed end to its discharge end. Thus, deck surface 19a slopes from its feed to its discharge end, providing for gravity flow therealong of the stream of pulp supplied to feed box lll. The degree of slope will vary depending upon the material being treated, although a slope of 11A inches per foot relative to the horizontal has been found to be satisfactory for most instances of use.

In order to avoid hang-up and caking of the concentrates caught by the trough 2l, wash water is supplied constantly at the upper end of such trough by means of one of the water supply pipes l5 during operation of the apparatus.

It is desirable that the gravity concentrator unit l@ be mounted for rocking movement from side to side during operation. Such rocking movement minimizes eddy currents, retards the speed of flow, and insures effective transverse distribution of the pulp across deck surface 19a. It also effects a beneficial washing and scrubbing action transversely of trough 2l.

To this end, the unit is here illustrated as hinged to the structural supports 23 by means of hinges 24. Rocker mechanism, shown here as comprising a bell crank 25 and drive link 26, serves to rock the several concentrator units lt) of each tier from side to side. The several rocker mechanisms are actuated in common by any suitable drive arrangement, for example by a drive rod 27, Fig. 8, eccentrically pivoted to the drive shaft of electric motor 2? and pivotally connected along its length to the several bell cranks 25.

The drive links 26 extend transversely of thev several concentrator units of the respective tiers, being articulatively attached thereto by pivoting, at 29, Fig. 3, to a superstructure 36 provided for each of the units.

It is almost essential that the slotted bottom wall 19 of gravity concentrator unit l0 be subjected to vibration during operation of the apparatus, so as to constantly keep the very narrowrecovery slits free andclear for the passage downwardly therethrough ofheavy values which tend to hug the eck surface wa. v

Vibration of short amplitude, for example, 15/1600 of an inch, is advantageously applied by rigidly attaching a conventional electromagnetic vibrator 3i to the top of each concentrator lil by a suspension bracket 32 bridging the deck 19 and aflixed to the side Walls i8.

With the concentrator unit lll vibrated during operation as indicated, the individual slat plates Ztl assume respective vibration characteristics of their own, and tend to whip differentially relative to each other, which further aids in keeping the very narrow slit openings -22 continually clear for the passage of the desired gravity concentrates therethrough.

It should be noted that the solid particles in the .pulp are kept more or less in suspension and separated from one another by the dynamic character of the flowing stream of pulp as it passes over and along the deck surface 19u, thereby giving the force of gravity an opportunity to act on each particle differentially to best advantage. Actually, gravity differentiation is most pronounced as between the individual particles and the liquid carrier therefor, so that maximum opportunity existsvfor particles of greatest specific gravity to drop freely to the bottom of the flowing stream into the interface 'zone between deck surface 19a and the liowing stream. Each slit opening 22 tends to bleed off particles of heaviest specific gravity, together with a minimum of the liquid carrier.

In keeping with the above it is a purpose of the invention to minimize eddy currents. The feed boxes 14 aid in achieving this purpose, for the several feed lstreams 3S, Fig. 8, are directed against either the back wall 14a or the bottom wall 14h of the respective boxes and fan out in all directions, whereby a thin sheet of the liquid pulp is passed to the deck surface i941 of each concentrator unit. The rocking movement and the vibration mentioned hereinbefore also aid in minimizing if not entirely eliminating eddy currents.

While dimensions are a matter of proper design for any given material and desired production capacity, we have had considerable success with a pilot plant wherein the deck of each concentrator unit is substantially five feet long and one foot wide fabricated by welding twenty slat plates, of eighteen gauge stainless steel three inches wide and twelve inches long and one eighth of an inch thick, to a trough structure of ordinary steel plate. The slit openings between adjoining plates are of inverted and truncated V-formation with the truncated portion extending downwardly frorn the deck surface a distance of 1/32 of an inch.

Whereas this invention is here illustrated and described with respect to a specific embodiment thereof, it should be realized that changes may be made within the scope of the following claims, without departing from the essential contributions to the art made by the teachings hereof.

We claim:

l. A gravity concentrator, comprising an elongate deck structure defining a flat and smooth deck surface arranged for traversal, longitudinally, by a liquid pulp containing solids to be concentrated, said deck surface having a feed end and a discharge end and sloping downwardly from said feed end to said discharge end so that the liquid pulp will flow thereover under the influence of gravity; means defining a longitudinal series of mutually spaced, transversely extending, attenuate, slit openings at said deck surface' and extending through'said deck structure, each of said slit openings having width at the deck surface within the range of approximately '071000 to approximately 15/1000 of an inch and having effectively increased width along its depth to prevent plugging, said slit openings being adapted to bleed off fine solid particles of high specic gravity that tend to descend to and hug said deck surface, said deck structure being largely imperforate and being free of obstructions so as to support and permit the unbroken ilow thereover of the bulk of said pulp, and the thickness of said deck structure being considerably less than lthe distance between successive slit openings; and means below said deck structure for catching the concentrate that is bled off.

2. The gravity concentrator of claim 1, wherein the respective slit openings are of approximately inverted V-formation in transverse section.

3. The gravity concentrator of claim 2, wherein the inverted V-formation is truncated.

4. The gravity concentrator of claim 3, wherein the deck structure comprises a longitudinal series of transversely extending Slat plates spaced slightly apart to define the slit openings.

5. The gravity concentrator of claim 4, wherein means are provided for vibrating the deck structure as the liquid `pulp traverses its deck surface.

6. The gravity concentrator of claim 5, wherein the means for catching the concentrate bled ol from the owing stream is an elongate trough structure extending longitudinally with the deck structure and rigidly joined thereto for vibration therewith.

7. The gravity concentrator of claim l, wherein a feed box is secured at the feed end of said deck structure, said feed box having a bottom forming a continuation of the deck surface.

8. The gravity concentrator of claim 1, wherein the deck structure comprises a longitudinal series of transversely extending slat plates spaced slightly apart to define the attenuate, slit openings; and supporting means to which opposite ends of said slat plates are rigidly secured.

9. The gravity concentrator of claim 8, wherein the supporting means comprises an elongate longitudinally extending trough, above the bottom and to the sides of which the slat plates are secured.

10. A gravity concentrator plant, comprising a plurality of gravity concentrator units arranged in tiers, each of said concentrator units comprising an elongate deck structure defining a at and smooth deck surface arranged for traversal, longitudinally, by a liquid pulp containing solids to be concentrated, said deck surface having a feed end and a discharge end and sloping downwardly from said feed end to said discharge end so that the liquid pulp will flow thereover under the inuence of gravity, means defining a longitudinal series of mutually spaced, transversely extending, attenuate, slit openings of said deck surface and extending through said deck structure, said slit openings have width at the deck surface within the range of approximately V1000 to approximately 1%000 f an inch, for bleeding off line solid particles of high specic gravity that tend to descend to and hug said deck surface, said deck struc-ture being largely imperforate and being free of obstructions so as to support and permit the unbroken ow thereover of the bulk of said pulp, and the thickness of said deck structure being considerably less than the distance between successive slit openings, and an elongate trough structure disposed below and extending longitudinally with the deck structure and serving as a launder for catching and discharging the concentrate that is 4bled off through the deck structure, the unit or units of each tier above the bottom tier having the discharge end of the deck surface directed to waste and the trough structure disposed to discharge into the feed end of the unit or units of the next lower tier.

11. The gravity concentrator plant of claim 10, wherein a water supply system is provided with branch lines running to those ends of the trough structures, respectively, which are disposed below the feed ends of the corre sponding deck surfaces and arranged to direct ow of water along said trough structures for flushing and rer pulping lthe concentrate that is bled off through said deck structures.

12. The gravity concentrator plant of claim 11, where- References Cited in the le of this patent UNITED STATES PATENTS 582,669 McKinnon May 18, 1897 645,533 Mauldin Mar. 13, 1900 685,773 Lewis Nov. 1, 1901 745,949 Wright Dec. 1, 1903 775,948 Stebbins Nov. 29, 1904 828,715 Cook Aug. 14, 1906 1,135,754 Bell Apr. 13, 1915 1,428,392 Ogden Sept. 5, 1922 1,779,202 Winston Oct. 21, 1930 1,973,770 McCullough Sept. 18, 1934 2,061,812 Slater Nov. 24, 1936 2,228,607 McDonald Ian. 14, 1941 2,348,479 Kellerman May 9, 1944 2,436,630 Clegg Feb. 24, 1948 2,780,356 Hobart Feb. 5, 1957 

